In a saucepan, add the sugar, milk, cocoa and salt. We beat to integrate and heat over medium heat while stirring. When the mixture reaches Boiling point we check the temperature with a kitchen thermometer, it has to reach 110 ºC.
We cook at this temperature for six minutes, stirring so that it does not stick to the base and burn. Handheld thermometers are less reliable than those that clip onto the rim of the saucepan, so avoid them if you can. We did not have another and the mixture was more tender than it should have been, but just as delicious.
Remove the saucepan from the heat and add the chocolate, previously melted, the peanut butter and the vanilla extract. Also add the oat flakes and mix well for a few minutes until start to thicken.
Drop spoonfuls of the dough onto a parchment-lined tray and flatten slightly. Let it cold down for an hour or until firm to the touch. If we do not consume them at the moment, we store them in an airtight container in the fridge, where they last up to a month.